Sequential Doping of Ladder-Type Conjugated Polymers for Thermally Stable n-Type Organic Conductors
Suhao Wang, Tero‐Petri Ruoko, Gang Wang, Sergi Riera‐Galindo, Sandra Hultmark, Yuttapoom Puttisong, Fabrizio Moro, Hongping Yan, Weimin Chen, Magnus Berggren, Christian Müller, Simone Fabiano
Abstract
Doping of organic semiconductors is a powerful tool to optimize the performance of various organic (opto)electronic and bioelectronic devices. Despite recent advances, the low thermal stability of the electronic properties of doped polymers still represents a significant obstacle to implementing these materials into practical applications. Hence, the development of conducting doped polymers with excellent long-term stability at elevated temperatures is highly desirable. Here, we report on the sequential doping of the ladder-type polymer poly(benzimidazobenzophenanthroline) (BBL) with a benzimidazole-based dopant (i.e., N-DMBI). By combining electrical, UV-vis/infrared, X-ray diffraction, and electron paramagnetic resonance measurements, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, and microstructure of the sequentially doped polymer films as a function of the thermal annealing temperature. Importantly, we observed that the electrical conductivity of N-DMBI-doped BBL remains unchanged even after 20 h of heating at 190 °C. This finding is remarkable and of particular interest for organic thermoelectrics.